Police said the majority of those arrested were Celtic fans, although it is believed that supporters from other clubs were also involved.

'At the end of the afternoon a large group of Celtic supporters attacked police officers in plain clothes,' a spokesman said.

'Eight were injured and one was knocked unconscious.

'A few of them had broken noses and needed stitches above their eyebrows and on their lips.

'Bottles and sticks were used in the attack which came out of nowhere.

'There were 15 arrests, mostly Celtic supporters.'

Calm before the storm: Celtic fans have a pre-match party in Amsterdam before their game with Ajax

Celtic lost the match 1-0 and face an uphill battle to reach the knockout stages of the competition.

Amsterdam Police said it expected the number of 15 arrests to rise during the night and that a final figures would be 'high'.

It is thought that fans from other European clubs were involved, although police said they 'had kept themselves covered'.

Celtic
supporters had been urged by the club to be careful after an attack on
Hoops supporters in a city-centre bar on Tuesday night.

Thousands of Celtic supporters flooded into Holland for the Group H game at the Amsterdam ArenA.

Riot gear: Police, equipped with shields and batons, try to contain some supporters in Dam Square

Hold off: One fan gestures towards an incoming police officer from his knees

A
statement on the Celtic website said: 'Celtic Football Club is urging
all supporters in Amsterdam for tonight's UEFA Champions League tie with
Ajax to be extra vigilant following an unprovoked attack on Celtic fans
last night

'The attack in the city centre by an element of the Ajax support resulted in a number of arrests.

'Celtic
are urging all supporters to be extra vigilant in the city centre and
at the Amsterdam ArenA, and to only stick to the advised areas for
safety reasons.'

At the
pre-match media conference on Tuesday afternoon, Ajax coach Frank De
Boer expressed hope that the tiny percentage of fans he describes as
"crazy" would not disrupt the game.

As thousands of supporters arrived in Holland, there were reports of violence after a gang of Dutch hooligans attacked a city centre pub where many had gathered. Throughout the day, there had been an uneasy truce in the city centre.

However, the mood quickly turned ugly when scores of riot police arrived in the area to marshal fans towards the stadium on the outskirts of Amsterdam.

Supporters set off flares and green smoke bombs outside the Dutch Royal Palace.Shortly before 5pm, the police moved in on the Celtic fans, using dogs and horses to clear the square.

Ushered: This Celtic supporter is moved along by a police officer in the Dutch city